Although long-term [small beta]-blocker therapy has been found beneficial in patients after an acute myocardial infarction, these drugs are greatly underused by clinicians. Moreover, the dosages of [small beta]-blockers used in randomized controlled trials appear to be much larger than those routinely prescribed.Objective
To determine whether an association exists between the dosage of [small beta]-blockers prescribed after a myocardial infarction and cardiac mortality.Methods
We performed a retrospective cohort study of 1165 patients who survived an acute myocardial infarction from January 1, 1990, through December 31, 1992. These patients represent a subgroup of the 6851 patients hospitalized at northern California Kaiser Permanente hospitals.Results
Of the 37.7% of patients prescribed [small beta]-blocker therapy, 48.1% were treated with dosages less than 50% of the dosage found to be effective in preventing cardiac death in large randomized clinical trials (lower-dosage therapy). Compared with patients not receiving [small beta]-blockers, those treated with lower-dosage therapy appeared to have a greater reduction in cardiovascular mortality (hazard ratio, 0.33; P=.009) than patients treated with a higher dosage (hazard ratio, 0.82; P =0.51), after adjustment for age, sex, race, disease severity, and comorbidities.Conclusions
The dosages of [small beta]-blockers shown to be effective in randomized trials are not commonly used in clinical practice, and treatment with lower dosages of [small beta]-blockers was associated with at least as great a reduction in mortality as treatment with higher dosages. This suggests that physicians who are reluctant to prescribe [small beta]-blockers because of the relatively large dosages used in the large prospective clinical trials should be encouraged to prescribe smaller dosages.